Radio frequency environment object monitoring system and methods of use

ABSTRACT

A method and apparatus for monitoring untagged objects in a target area including calibrating a radio environment monitoring system including a rules engine and a baseline data set for a target area by recording a set of changes to the RF environment fingerprint of the target area received by the radio environment monitoring system as the target area is filled with objects. During system operation, scanning the target area with the radio environment monitoring system for a current RF environment fingerprint, comparing the current RF environment fingerprint with the baseline data set by a rules engine and reporting an output of the rules engine.

BACKGROUND

1. Field of the Invention

This invention relates to a radio frequency environment monitoringsystem for object presence feedback. More particularly, the inventionrelates to a radio frequency environment monitoring system for RFIDtagged and/or untagged object monitoring via analysis of changes to themonitored RF environment occurring as the objects present in themonitored area are varied in position and or number.

2. Description of Related Art

Previous RFID tag inventory and or object passage gateway monitoringsystems have relied upon reading one or a plurality of tags, each tagrepresenting a unit or known quantity of units of associated objects.

It is not practical to apply an RFID tag to each object to be monitored,and/or it is desirable to monitor the presence of quantities of theobjects to be monitored with greater precision than just a binaryindication of an RFID tag associated with a quantity of objects each ofwhich may or may not be tagged, as might be the case with itemscontained in a parts bin.

In prior RFID portal systems, RFID readers monitor RFID tags attached toobjects and/or object loads during passage through, for example, anumber of dock doors in a distribution center. Because of the nature ofknown RFID systems it is not always possible to determine whetherparticular tags are in a particular door. It is possible for example fora reader in door 2 to read a tag in door 1 or door 3. Without specialdoor sensors, it is not possible to determine whether a particular dooris open or closed and whether an object is moving out of thedistribution center or into the distribution center.

Further, many items have packaging that is not complementary to beingtagged, such as metal cans and/or plastic bottles, such as soft drinks.Also, it is not economical to tag individual items, such as nails,bolts, batteries, coins or the like. To optimize inventory operations,for example for Just In Time inventory systems, it is required to knowthe rate of depletion and/or when inventory of a specific item is aboutto be depleted, before actual depletion occurs.

Therefore, it is an object of the invention to provide an objectmonitoring solution that overcomes deficiencies in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention,where like reference numbers in the drawing figures refer to the samefeature or element and may not be described in detail for every drawingfigure in which they appear and, together with a general description ofthe invention given above, and the detailed description of theembodiments given below, serve to explain the principles of theinvention.

FIG. 1 is a schematic block diagram of an exemplary radio environmentmonitoring system according to the invention.

FIG. 2 is a schematic diagram demonstrating reference tags in a targetarea and a pair of cooperating RF transmitter-receiver/beamsteering/antenna assemblies positioned to scan the target area.

FIG. 3 is a schematic diagram demonstrating signal paths with respect toreference tags in a target area detected by an antenna within a targetarea, the target area filled with untagged objects.

FIG. 4 is a schematic diagram according to FIG. 3, with one half theuntagged objects removed.

FIG. 5 is a schematic diagram according to FIG. 3, with all of theuntagged objects removed.

FIG. 6 is a schematic diagram of a signal processor and a functionprocessor module.

FIG. 7 is a schematic diagram of a dual antenna embodiment generatingsignal inputs for the processing unit.

FIG. 8 is a schematic diagram of a processing unit including a rulesengine.

FIG. 9 is a schematic graphical representation of an instantaneoussignature of a target area location with respect to signal level andfrequency.

FIG. 10 is a schematic graphical representation of the instantaneoussignature of FIG. 9, with respect to phase angle and frequency.

FIG. 11 is a schematic graphical representation of an averagesub-signature derived from sampling the instantaneous signature of thetarget area location of FIG. 9 over an extended time period.

FIG. 12 is a schematic graphical representation of the averagesub-signature of FIG. 11, with respect to phase angle and frequency.

FIG. 13 is a schematic graphical representation of backgroundenvironmental noise at a target area location with transceivers of theITCS turned off.

FIG. 14 is a schematic graphical representation of the RF environmentfingerprint, with respect to signal level and frequency, obtained from atarget area as it is successively scanned when initially empty ofuntagged objects.

FIG. 15 is a schematic graphical representation of the RF environmentfingerprint of FIG. 14, with respect to phase and frequency.

FIG. 16 is a schematic graphical representation of the RF environmentfingerprint, with respect to signal level and frequency, obtained fromthe target area of FIG. 14, as it is successively scanned when one halffilled with untagged objects.

FIG. 17 is a schematic graphical representation of the RF environmentfingerprint of FIG. 16, with respect to phase and frequency.

FIG. 18 is a schematic graphical representation of the RF environmentfingerprint, with respect to signal level and frequency, obtained fromthe target area of FIG. 14, as it is successively scanned when one halffilled with untagged objects.

FIG. 19 is a schematic graphical representation of the RF environmentfingerprint of FIG. 18, with respect to phase and frequency.

DETAILED DESCRIPTION

The inventor has recognized that the entirety of the monitored radiofrequency environment, hereafter referred to as the RF environmentfingerprint, may be used to derive changes of object presence and/orlocation(s), even where the individual objects within the target areaare not each provided with their own individual RFID tag.

It is possible to monitor the presence and/or direction of movement ofan RFID tag within a three dimensional target area via RFID monitoringsystems. For example, International Patent Application serial numberPCT/US08/58824, titled “Radio Frequency Signal Acquisition and SourceLocation System” filed Mar. 30, 2008 by Bloy et al, and InternationalPatent Application serial number PCT/IB2008/053643, titled “SteerablePhase Array Antenna RFID Tag Locater and Tracking System”, filed Sep. 9,2008 by Bloy, both applications commonly owned with the presentapplication and hereby incorporated by reference in their entirety,describe systems of cooperating steerable phased array antennasperforming beam scans of a target area, via an electronic beam steeringcircuit such as an array of phase shifters coupled to a correspondingarray of antenna elements of a panel antenna, from which the presenceand location of individual RFID tags is derived by logical processing ofhistorical signal data obtained from prior scans of the target area.

To derive the location of the RFID tags, the RF signal intelligenttracking and control system (ITCS) of PCT/US08/58824 processes aplurality of signals received in response to a scanning narrow beaminterrogation signal directed through the target area to derive whichare true signals received directly from an individual RFID tag and whichare pseudo emitter reflections of the same RFID tag response signal(carrying the same RFID tag identifier) reflecting off of secondarysurfaces before finally reaching an antenna. The received signalinformation may be processed to reject the pseudo emitters, thusidentifying the signal response to focus three-dimensional locationroutines upon, thereby identifying the RFID tag position in threedimensions. The identified RFID tag locations may be combined togenerate a three dimensional picture of each of the RFID tag locationsin the target area and, over time, the movement if any of the RFID tags.

Further, the ITCS may apply highly focused and/or varied interrogationsignal power, for example to penetrate adjacent objects and/or packagingsurrounding a specific RFID tag.

An ITCS includes an electronically steerable phase array antennaconnected to a phase shift network and a radio frequencytransmitter-receiver unit. For purposes of the present invention, thetransmitter-receiver unit may or may not be specifically configured foridentifying, tracking and locating RFID tags. The transmitter-receiverunit may contain circuit and/or logic capabilities to perform, incooperation with an electronic steering circuit and antenna, functionssuch as:

-   -   transmission of a continuous wave signal    -   modification and/or modulation of the continuous wave signal    -   reception of a return signal    -   demodulation of the return signal    -   return signal signal strength measurement    -   time delay measurement between a transmitter signal and the        return signal    -   phase measurement of the return signal compared with the phase        of the transmitter signal; and    -   reporting the strength, relative phase and time delay of the        returned signal.

The transmitter-receiver unit is under the control of and providesreceived signal information to a processing unit that may be local to orremote from the antenna and/or transmitter-receiver. The processing unitcauses the transmitter-receiver to transmit a continuous wave signal andfurther causes the continuous wave signal to be modified/modulated asdesired. The processing unit also commands the electronic steeringcircuit, either directly or via a communications link to a dedicatedelectronic steering sub-processor/controller, to direct the beam emittedfrom the steerable phased array antenna into different directions, forexample directing the beam direction through a raster scan or the likeof the target area. At each point or position of the beam an outputreport of the transmitter-receiver unit is passed to the processorcontaining, for example:

-   -   a scan direction and time code;    -   refractive frequency index of any RFID tag(s) detected;    -   relative phase and time delay;    -   Return Signal Strength Indicator (RSSI)—the coverage or lack of        coverage of the RFID tag by objects will change the RSSI (a        delta of signal absorption); and    -   multipath pseudo emitter shift (error)—the multiple pseudo        reflections and their monitored location will change as the        position and or coverage of the signal source by other objects        changes.

The output report may be stored in a memory, register or table that maybe temporary or permanent, hereafter referred to as the data matrix.

As disclosed in PCT/US08/58824, the ITCS is able to detect so calledpseudo emitters and use multi-path ambiguity resolution algorithms toreduce or eliminate positional ambiguity these signals introduce whenattempting to identify the locations of RFID tagged items in a targetarea. While the prior ITCS RFID tracking and location systems includedextensive logic dedicated to the identification and rejection of thesepseudo emitter signals, the present invention recognizes that thesesignals, especially when their appearance, location and/or disappearanceis tracked over time as part of the overall RF environment fingerprintpresent in a target area, may be interpreted as an object presenceand/or location indicator for untagged objects within the target area.

As shown in FIG. 1, an exemplary system according to the invention is avariation of an ITCS including a plurality of antenna(s) 7 coupled to atransceiver 2. The antenna(s) 7 providing a signal beam steerable via aseparate or integrated beam controller directed by the transceiver 2and/or processor 1. The processor unit 1 also includes a rules engine 3operating in concert with the normal ITCS processor functions upon thepresent RF environment fingerprint and a collection of baselineconfiguration data, for example stored in a data matrix 5 of theprocessor unit 1. Alternatively, the ITCS may include multipletransceiver(s) 2, each dedicated to a separate or multiple antenna(s) 7.System commands are input and results are output via an operatorinterface 4

The rules engine 5 compares the real time RF environment fingerprintwith a set of baseline calibration RF environment fingerprint data setsto identify pseudo emitter and/or response signal degradationindications of changes to the number and/or position of untagged objectspresent in the target area. Resolution of the location, pseudo emitterand/or response signal degradation indications is greatly increased whenmultiple antenna(s) 7 of the ITCS are arrayed about the target area 9,for example as shown in FIG. 2. At least two antenna(s) 7 enabling theapplication of triangulation logic between a beam vector of each antenna7 to generate an accurate z-axis position parameter of signal sourcesuseful alone or as a further accuracy check upon z-axis estimatesderived from signal timing routines.

The rules engine 3 operates upon two primary indications of an untaggedobject(s) 11 presence in the target area 9, demonstrated in FIGS. 3-5.First, in a line of sight parameter 13, the response signal from areference RFID tag 15, will become measurably degraded and/or cut offentirely as untagged object(s) 11 and/or structures 17 occur in and/orare placed in the signal path between the reference RFID tag 15 and anantenna 7, for example covering and/or obscuring the signal path to areference RFID tag 15, thereby identifying the presence of an untaggedobject 11 along a signal path between the reference RFID tag 15 and anantenna 7. The reference RFID tag(s) 15 may be passive RFID tagspermanently attached around the target area 9, for example on thefloors, shelving and/or ceiling of a storeroom, warehouse or other spaceto be monitored. Second, in a pseudo emitter parameter 19, untaggedobjects and/or structures 17 including RF reflective surfaces (metaland/or metal coated surfaces) occurring and/or placed proximate areference RFID tag 15 signal path will generate pseudo emitter responseswith respect to that RFID tag 15 that may be located in three dimensionswithin the target area 9 as if they were RFID tags, themselves. Further,where separate antenna(s) 7 are arrayed about the target area 9, thedifferent lines of sight between each antenna 7, various reference RFIDtag(s) 15 and an untagged object 11 may generate both line of sightsignal parameter 13 and pseudo emitter parameter 19 responses withrespect to the same untagged object(s) 11, greatly improving the rulesengine accuracy (for diagram clarity, representative signalpaths/parameters are diagrammed with respect to only one of the antenna7).

In an exemplary embodiment of the invention, the signals received fromthe ITCS in real time and/or as accessed from the ITCS data matrix 5include the following signal parameters applied as inputs to signalprocessor(s) 11 integrated with and/or coupled to the processor unit 1:

-   -   The phase φ of a received signal at an instant in time t_(i);    -   the amplitude of the received signal at the same instant in time        t_(i);    -   a fast Fourier transform (FFT) of the received signal envelope        at the same instant in time t_(i;); and    -   a time reference.

The resolution and accuracy of the time reference is preferably veryhigh, for example derived from an atomic clock, GPS signal or the like.The signal processor(s) 11 output a time coded signature (sig) which isa unique signal signature for time t, generated by the signals receivedby the ITCS from each of the antenna(s) 7 along a known antenna signalbeam orientation, stored as a mathematical representation, for exampleresulting from FFT processing of frequency and phase, as well asfrequency and amplitude signal data. Where multiple antenna(s) 7 areapplied, the target spatial coordinate where the antenna signal beamsare directed to intersect may be applied to each signal record as aspecific three-dimensional reference location of the signal signatureobtained.

The signal signature feeds a function processor 23 which may be aseparate component coupled with or an internal logical function of theprocessor unit 1. The function processor 23 derives and outputs arunning average sub-signature f(sig), from a plurality of samples of thetime coded instantaneous signature (sig) received by the functionprocessor 23 over an observation period.

The observation period may be varied by the processing unit 1 to takeaccount of changes in the environment or other user defined parameters.A plurality of sub signatures is further processed by the processingunit 1 to derive two further signatures, a primary signature and areference signature for each spatial coordinate.

FIG. 6, demonstrates signal/data flow through a basic signal processor21 and function processor 23 module. As shown in FIG. 7, multiple signalprocessor(s) 21 and function processor(s) 23 modules may be applied, forexample each fed by signals from a different antenna 7. Signalsgenerated by signal processor(s) 21 and function processor(s) 23 aremathematically summed by respective summing processor(s) 25 to produce acomposite running average sub-signature f(sig) and instantaneoussignature (sig). These two signatures represent a unique instantaneoussignature (sig) and a running average sub-signature f(sig) for a knownlocation within the target area 9. Thus, the data matrix 5 may be loadedwith a signal signature representing the signal response for each of aplurality of unique spatial positions within the target area 9 of theITCS. The system is explained herein with reference to a two antennasystem. One skilled in the art will appreciate that the system resultwill improve as additional antenna's and associated signal processor andfunction processor modules are added to the ITCS.

As shown in FIG. 8, the processor unit 1 may be selected to havesignificant processing power for both mathematical and signalprocessing.

In its most simple form, the processor unit 1 receives two inputs from asingle signature generator, average sub-signature f(sig) and (sig) forthe X and Y (azimuth and elevation) coordinates of the point in spacefrom which the signature was derived. This information is stored in thedata matrix 5. The processor unit 1 causes the beam steered antenna(s) 7to scan the environment in steps whose size depends on the beamillumination, preferably such that there is a slight overlap betweensteps. This can be best understood by picturing a flashlight being sweptacross a wall. The flashlight is moved a step at a time. At each stepthe light is momentarily switched on and a picture taken. The flashlightis moved and the light is again momentarily switched on such that theilluminated patch slightly overlaps the previous patch. This process isrepeated in a raster scan until the entire wall has been examined. Aseries of measurements is made for each beam position and the averagesub-signature f(sig) and (sig) for each spatial point is recorded in thedata matrix 5 with the X,Y or where known, X,Y,Z position of the targetpoint in space.

A recording cycle may be defined as one complete sweep of the targetarea 9. The processor unit 1 causes a plurality of recording cycles tobe undertaken to build a running average for an average sub-signaturef(sig) of each spatial location that may be further processed to derivean updated reference signature for each spatial location. The referencesignature (Ref sig) is an average of many primary signatures and is usedas a reference for determining whether change has occurred in theenvironment. Thus, the data matrix 5 may be updated with each sweep ofthe target area 9.

In addition, the reference signature (Ref sig) may also include asignature of the background Radio Frequency noise and or signals withthe interrogator switched off, i.e. the background RF noise due tosources other than the primary emitter. This background signature isused by the processor to specifically exclude environmental changes dueto Radio Frequency sources not generated by the system of thisinvention. These noise sources may include but are not exclusively dueto transmissions or emitters such as TV or mobile radio base stations,Cellular base stations, low power and Part 15 devices operating in thesame radio neighborhood, etc. as well as unintentional radiators such ascomputing and other non radio transmitting devices.

To improve signal quality, the background noise signature may besubtracted from any of the other signatures, such as the instantaneoussignature, the average signature and the running reference signature, aprocedure referred to as noise canceling.

For the purposes of further explanation reference will be made to asingle spatial point. One skilled in the art will appreciate thatsimilar processing may be applied to each spatial point and/or a seriesof partially overlapping points in the target area to derive a changeanalysis and thus inventory of the entire target area by extension ofthe single point processing disclosed hereafter.

The processor unit 1 uses three pieces of information to determine achange in the environment and measure the magnitude and nature of thechange. The change analysis is then routed to a “rules” engine 3 whichthen takes action based on the nature of the change and pre-determinedor preset user requirements.

The three pieces of information used are:

-   -   The instantaneous signature (sig) representing a single sample        of a single point in the environment,    -   the average sub-signature f(sig) of the same point; and    -   the reference signature for the same point in space.

The processor unit 1, compares the instantaneous signature (sig), forexample as represented graphically with respect to frequency and signallevel in FIG. 9 and contemporaneously with respect to phase angle withrespect to frequency in FIG. 10, with the values of the averagesub-signature f(sig), for example as graphically shown in correspondingFIGS. 11 and 12, in a comparator processor 27 in order to determinewhether the instantaneous signature (sig) is within preset limits. Inother words the average sub-signature f(sig) is used to check thevalidity of the instantaneous signature (sig) to make sure that it wasnot a spurious read or a one-time aberration. As described herein aboveeach of these signatures, also referred to as RF fingerprints, may alsobe processed to subtract the background environmental noise that may bepresent, for example as graphically represented by FIG. 13. The resultof this check is a primary signature (sig prime) for that particularpoint in space.

The primary signature (sig prime) is then compared with the referencesignature from the data matrix 5 in a further comparator processor 27.If there is a significant change, then the resulting nature of thechange is routed to the rules engine 3, which triggers the appropriateaction according to the established rules framework. If there is nosignificant change, then it is assumed that the environment has remainedstable over the preceding period of time. The method using two antennasystems is the same. However because there are two steerable beam basestations, it is possible to more accurately determine a point in spaceusing the azimuth and elevation positions from the two base stations toderive X, Y and Z positional information via triangulation. Further,dual (or more) signal beams intersecting at a desired location increasethe interrogation signal intensity, for the desired point of interest,without radiating RF power beyond established limits, outside of thetarget area 9.

Baseline calibration RF environment fingerprint data is collected duringsystem configuration to represent a range of possible target area 9configurations, for example of the target area 9 entirely empty ofuntagged objects 11, and then in multiple instances as the target area 9is successively filled with target objects.

FIGS. 14-19 graphically demonstrate a simplified set of representativesignals from which RF environment fingerprint obtained from the sametarget area 9 as it is successively scanned either during initialcalibration sweeps and/or during area monitoring, for example wheninitially empty of untagged object(s) 11 (FIGS. 14, 15), half of theuntagged object(s) 11 removed (FIGS. 16, 17) and finally fully filledwith the untagged object(s) 11 (FIGS. 18, 19). In the entirely emptystate, pseudo emitter signal parameters 19 related to structure(s) 17 ofthe target area 9, identified by their longer interrogation tobackscatter response signal reception time delay (resulting from alonger signal path via, for example, reflective surfaces of supports andor shelves) may be mapped for later exclusion from rules engine pseudoemitter parameter 19 signal location/processing. Once an “empty” RFenvironment fingerprint of a target area 9 has been mapped, furtherchanges to the RF environment fingerprint may be recorded, associatedwith known events, such as the appearance and location of dynamic pseudoemitter signal responses that appear/disappear during calibratedre-stocking and/or depletion of specific tagged and/or untaggedobject(s) 11 within the target area. Multiple RF environmentfingerprint(s) obtained during each calibration step and also duringongoing real time monitoring may be averaged to improve accuracy and/ordiscard erroneous data points.

Dynamic pseudo emitter signals may be further identified with theassistance of signal specific scans of the target area 9. For example,while an interrogation signal is focused upon a particular locationknown to include a reference RFID tag 15 or other response signalsource, the entire target area 9 may then be scanned to identify thelocations of any associated pseudo emitter parameter 19 signals that mayhave appeared or disappeared since the last RF environment fingerprintwas scanned.

In addition to purely radio frequency inputs from within the target area9, the qualified appearance and/or disappearance of specific tagidentifications within the monitored RF environment may be used todynamically and automatically determine actions to be taken by the RFenvironment monitor, such as altering the coverage pattern to sweepparticular areas in a predetermined manner. For example, in oneembodiment of the system, a known reference RFID tag 15 is attached tothe lower edge of each of a plurality of dock roller-doors such that asthe door is opened the reference RFID tag 15 rises from the floor to thetop of the opening. The radio environment monitor observes and monitorsthe position of the door reference RFID tag 15 of each door as well asthe location of individual tags on items or objects in the vicinity ofeach of the dock doors. The rules engine is configured to recognizethese changes to the target area access and further apply an associationbetween an individual dock door and the items that should be loadedthrough the dock door. If the dock door is opened when it should not beopen or if the incorrect items are loaded through the dock door then anaction may be triggered.

In an environment in which objects are stocked on shelves or movablepromotional display modules, as might typically be the case in a groceryretail store for example, the baseline data set of the target area 9 RFfingerprint may include a scan of a target area 9 including a higherresolution focus on individual storage shelving on which a plurality ofreference RFID tag(s) 15 are arrayed. The baseline data set identifiespositions of each of the reference RFID tag(s) 15, as well as any staticpseudo emitter parameter 19 signals generated by any RF reflectivesurfaces present in the target area when each of the shelves is empty ofthe untagged object(s) 11 to be monitored. As untagged object(s) 11 tobe monitored are then successively added to the shelves, the signalresponse characteristics of each of the reference RFID tag(s) 15attached to the shelves and/or wall(s) behind the shelves changes and/ornew pseudo emitter parameter 19 signals are introduced into the RFenvironment fingerprint by RF reflective surfaces of the untaggedobject(s) 11. Also, the baseline data set may include changing responsesignal absorption characteristics, if any, which may occur as theuntagged object(s) 11 to be monitored begin to cover and or obscure thereference RFID tag(s) 15 line of sight parameter 13 (the signal responsewith the shortest time delay between interrogation and backscattersignal response from an RFID tag, such as a reference RFID tag 15)and/or pseudo emitter parameter 19 signal paths with respect to one ormore of the antenna(s) 7.

By monitoring changes in the RF environment fingerprint, event rules maybe applied by the rules engine to generate user outputs and/or situationreports. For example, changes to stock presence and/or quantity in aspecific bin may be estimated; the bin presence and/or object quantitytherein may be tracked, for example generating reports of objects forwhich the inventory is running low. Thus inventory monitoring or thelike may be performed via RFID, without requiring an individual tag oneach object.

Large groups of tagged items may be similarly monitored by observing thenumber and location of signal responses received from a largeconcentration of RFID tagged objects, even if a significant number ofthe RFID tags are obscuring/covering one another and preventing themfrom being detected. Further any RFID tags affixed to objects within thetarget area 9, may be treated for purposes of the RF environmentfingerprint as reference RFID tag(s) 15, with any associated signaldegradation and or pseudo emitter data applied only as long as theseRFID tags are monitored to be in the position associated with theparticular RF environment fingerprint.

This baseline data set may be updated from time to time to compensatefor changes in the environment. The system may be configured toautomatically and dynamically update the baseline data set as smallchanges occur.

By monitoring the environment and comparing large changes to thereference RF environment fingerprint of the stored baseline data set,the system may compute that something in the target area 9 has changedand make a decision based on this change using the rules engine 3. Wheremultiple factors within the rules engine 3 indicate an objects presence,such as signal degradation and/or dynamic pseudo emitter parameter 19signal detection from multiple paths, reference RFID tag(s) 15 and/orantenna(s) 7, an increased probability factor may be assigned to theresulting rules engine 3 conclusion. Rules engine 3 conclusions may thenbe assessed depending upon their assigned probability factor totals andonly those meeting a threshold probability factor higher than a presetlevel output for pre-assigned action(s).

During the calibration procedure, specific shelf locations may beallocated to specific objects to enable monitoring and reporting uponthe presence of multiple separate object classes, corresponding forexample to different consumer products in a grocery store environmentand or multi-item distribution warehouse. If the system is furthercoupled to the electronic stock-keeping computer system, the change inthe RF environment fingerprint may be associated with items removed fromthe shelves and the rules engine 3 may then, for example, trigger apurchase order to be raised.

One skilled in the art will appreciate an advantage of the invention isthat objects may be tracked and located without a need to individuallytag them. By tagging the environment, for example the shelves and orobject bins instead of each individual object, and recording how the RFenvironment fingerprint, including pseudo emitter parameter 19 signalsassociated with desired objects, then changes as the target area 9 isfilled and/or emptied of objects, for example by comparison with abaseline data set, it is then possible to monitor the movement or changeof position of untagged objects in the target area 9 with significantprecision.

Table of Parts 1 processor unit 2 transceiver 3 rules engine 4 operatorinterface 5 data matrix 7 antenna 9 target area 11 untagged object 13line of sight parameter 15 reference RFID tag 17 structure 19 pseudoemitter parameter 21 signal processor 23 function processor 25 summingprocessor 27 comparator processor

Where in the foregoing description reference has been made to ratios,integers, components or modules having known equivalents then suchequivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin considerable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, representativeapparatus, methods, and illustrative examples shown and described.Accordingly, departures may be made from such details without departurefrom the spirit or scope of applicant's general inventive concept.Further, it is to be appreciated that improvements and/or modificationsmay be made thereto without departing from the scope or spirit of thepresent invention as defined by the following claims.

I claim:
 1. A method for monitoring untagged objects in a target area,comprising the steps of: calibrating a three dimensional radioenvironment monitoring system for a target area by recording a baselinedata set of changes to an RF environment fingerprint of the target areareceived by the three dimensional radio environment monitoring system asthe target area is filled with objects; each of a plurality of recordsof the baseline data set is averaged from multiple scans of the targetarea during a static object condition; scanning the target area with thethree dimensional radio environment monitoring system for a current RFenvironment fingerprint; comparing the current RF environmentfingerprint with the baseline data set by a rules engine; and reportingan output of the rules engine.
 2. The method of claim 1, wherein thebaseline data set includes changes to the RF environment fingerprintcaused by filling the target area with multiple objects in multiplepositions within the target area.
 3. The method of claim 1, wherein therules engine includes a line of sight parameter wherein a degradation ofa signal response from a reference RFID in the target area indicates thepresence of an object along a line of sight between the reference RFIDand an antenna associated with the signal response.
 4. The method ofclaim 1, wherein the rules engine includes a dynamic pseudo emitterparameter wherein a pseudo emitter that appears and or disappearscorrelates to an object being positioned at a known location accordingto the baseline data set.
 5. The method of claim 1, wherein the rulesengine includes a static pseudo emitter parameter wherein a signaldegradation of a static pseudo emitter correlates to an object beingpositioned at a known location according to the baseline data set. 6.The method of claim 1, wherein the rules engine output is an inventoryreport indicating that an inventory of an object has fallen below apreset amount.
 7. The method of claim 1, wherein the rules engine outputis coupled to an electronic stock keeping system that issues a purchaseorder for an object that has fallen below a preset amount.
 8. The methodof claim 1, wherein the RF environment fingerprint is averaged frommultiple scans of the target area.
 9. The method of claim 1, wherein therules engine applies a probability factor to an object presencedetermination.
 10. The method of claim 9, wherein the rules engine onlyoutputs object presence determinations that have a probability factorabove a preset level.
 11. The method of claim 1, wherein objects withRFID tags are included as sources of reference RFID tags during RFenvironment fingerprint monitoring.
 12. A method for monitoring untaggedobjects in a target area, comprising the steps of: calibrating a threedimensional radio environment monitoring system for a target area byrecording a baseline data set of changes to an RF environmentfingerprint of the target area received by the three dimensional radioenvironment monitoring system as the target area is filled with objects;scanning the target area with the three dimensional radio environmentmonitoring system for a current RF environment fingerprint; comparingthe current RF environment fingerprint with the baseline data set by arules engine; and reporting an output of the rules engine; wherein theappearance in the RF environment fingerprint of a registered referenceRFID indicates a change to the target area access.
 13. The method ofclaim 12, wherein the change to the target area access is the opening ofa door.
 14. A method for monitoring untagged objects in a target area,comprising the steps of: calibrating a three dimensional radioenvironment monitoring system for a target area by recording a baselinedata set of changes to an RF environment fingerprint of the target areareceived by the three dimensional radio environment monitoring system asthe target area is filled with objects; the baseline data set includingchanges to the RF environment fingerprint caused by filling the targetarea with multiple objects in multiple positions within the target area;scanning the target area with the three dimensional radio environmentmonitoring system for a current RF environment fingerprint; comparingthe current RF environment fingerprint with the baseline data set by arules engine; the rules engine including a line of sight parameterwherein a degradation of a signal response from a reference RFID in thetarget area indicates the presence of an object along a line of sightbetween the reference RFID and an antenna associated with the signalresponse; the rules engine including a dynamic pseudo emitter parameterwherein a pseudo emitter that appears and or disappears correlates to anobject being positioned at a known location according to the baselinedata set; the rules engine includes a static pseudo emitter parameterwherein a signal degradation of a static pseudo emitter correlates to anobject being positioned at a known location according to the baselinedata set; and reporting an output of the rules engine.
 15. The method ofclaim 14, wherein the rules engine applies a probability factor to anobject presence determination.
 16. The method of claim 15, wherein therules engine only outputs object presence determinations that have aprobability factor above a preset level.